Automobile radio apparatus



Jan. 25, 1938. w. RUNGE 2,106,159

AUTOMOB ILE RADIO APPARATUS iled Jan. 31, 1936 II% N INVENTOR. WILHELM RUNGE' BY 7% m ATTORNEY.

Patented Jan. 25, 1938 awaits AUTOMQBILE RADIO APPARATUS tion of Germany Application January 31, 1936, Serial No. 61,644 In Germany February 25, 1935 6 Claims.

This invention relates to new and novel transnutter-receiver apparatus, especially adapted for automobile signal purposes.

The present invention is concerned with a sending and receiving apparatus comprising change over means which is f d directly from the low voltage source of a vehicle and which is used for signalling from the car and between cars of similar kind.

It has been suggested in the prior art, for send ing a signal from a car about to pass a car travelling ahead of to send signals by means of electromagnetic Waves. For this purpose, each car must be fitted with a transmitter and a receiver. In order to reduce the space requirements and cost, radio apparatus which contains vacuum tubes having at least one radio frequencand one audio frequency stage is provided. In

the simplest form, a two-tube outfit is used, the first or input tube being connected when the apparatus is set in the receiving position to act as a. detector and the second tube being employed as an audio frequency amplifier. The filament voltages are directly derived from the car battery by a resistance voltage divider. The question of supplying the plate with potential may be solved in two different ways. Either the apparatus is furnished with space-charge grid tubes, in which case the voltage furnished from the ordinary car battery of six to twelve volts will be sufficient, or else the standard type tubes may be employed in which case it will be necessary to produce a high plate voltage by the aid of a direct current converter. In actual practice, vibrators with subsequent or simultaneous rectification have proved satisfactory.

Now, the idea underlying the present invention is to provide an arrangement for the detector tube which by feedback may be de-attenuated to a certain extent, an additional feedback whereby the tube can be caused to generate radio frequency oscillations. This additional feedback, if one is to be provided, is rendered inoperative while the switch is in the receiving position of the set. .1 Similarly, an audio frequency feedback is provided for the audio frequency amplifier which is likewise disconnected by a switch during receiving intervals.

If signals are to be transmitted by the said arrangement, both switches must be closed. The

detector tube is thus caused to act as a regenerative transmitter, while the audio frequency amplifier becomes a tonal oscillator adapted to modulate the transmitter tube. By means of another switch, simultaneously operated with the change-over to transmission, loudspeaker can be disconnected or be preferably short-ch cuited. For if that is not done the transmitted signal would be rendered audible in the loud speaker on the same car.

If desired, a tuned radio frequency stage could be added to the said two tube outfit, said radio frequency stage amplifying only the radio frequency oscillations and being intended to shut out disturbing noises and interfering actions having their sources in the electrical equipment of the car. In this enlarged outfit, the radio frequency feedback serving in. transmission must be established from the plate of the detector circuit to the circuit preceding the radio frequency amplifier in order that also in this instance the radio frequency oscillations will be modulated by the tonal frequency.

Figures 1 and 2 show by way of example circuit schemes adapted to practice the basic idea of this invention. Referring to Figure 1, A is an antenna which is used both for sending and receiving. D

is a demodulator stage whose input circuit is tuned to the radio frequency carrier wave. CH is a regenerative condenser which insures a feedback such that the demodulator stage will be caused to become self-oscillatory. This feedback is interrupted by a switch Sh whenever the outfit is to be used for reception. Coupled with the same demodulator stage D is an audio frequency amplifier stage N by way of a transformer '1. The output of this audio frequency stage is connected, if desired, by way of an output transformer with a loudspeaker L. The audio frequency amplifier is provided with a feedback condenser On by way of which audio frequency feedback is establishable. The frequency of course, is a function of the constants of the associated circuit elements, but by additional means it may be caused to assume any desired value. Also here a switch is provided as indicated at Sn by the agency of which the generation of tonal frequency is discontinued during receiving intervals.

Figure 2 shows a similar circuit scheme. The two switches Sh and Sn are combined in one switch Sr whose function is the same as in the circuit scheme Figure 1. Fig. 2 also shows the radio frequency input stage mentioned above.

I claim:

1. In a receiving and sending system comprising in combination an input and output circuit, a detector stage connected to said input circuit, an audio frequency amplifier stage connected to said detector stage, means for establishing a feedback in both the detector and audio stages,

switching means to interrupt said feedback in the detector stage, a second switching means to interrupt the feedback in said audio frequency stage, said first and second switching means being closed in the sending position and open in the receiving position.

2. In a receiving and sending system comprising in combination an input and output circuit, a radio frequency input stage connected to said input circuit, a detector connected to said radio frequency input stage, an audio frequency amplifier stage connected to said detector stage, means for establishing a feedback in both the detector and audio stages, switching means to interrupt said feedback in the detector stage, a second switching means to interrupt the feed back in said audio frequency stage, said first and second switching means being closed in the sending position and open in the receiving position.

3. In a receiving and sending system comprising in combination an input and output circuit, a detector stage connected to said input circuit, an audio frequency amplifier stage connected to said detector stage, means for establishing a feedback in both the detector and audio stages, a switch to interrupt the feedback in both the detector and audio frequency stages, said switch being closed in the sending position and open in the receiving position.

4. In a receiving and sending system comprising in combination an input and output circuit, a detector stage connected to said input circuit, an audio frequency amplifier stage connected to said detector stage, means for establishing a capacitive feedback in both the detector and audio stages, switching means to interrupt said feedback in the detector stage, a second switching means to interrupt the feedback in said audio frequency stage, said first and second switching means being closed in the sending position and open in the receiving position.

5. In a sending and receiving system comprising in combination a common antenna for both receiving and sending, a detector stage whose input circuit is tuned to a desired radio frequency carrier wave, an audio frequency amplifier stage connected to said detector stage, means for establishing a feedback in both the detector and audio stages, switching means to interrupt said feedback in the detector stage, a second switching means to interrupt the feedback in said audio frequency stage, said first and second switching means being closed in the sending position and open in the receiving position.

6. A receiving and sending system comprising an input and output circuit, a detector coupled to said input stage, an audio frequency stage coupled to said detector stage, capacitive feedback means connected to the output stage of both the detector and audio frequency stages, switching means to change said detector to a transmitting stage and said audio stage to an audio frequency generator to modulate said transmitter stage, said switching means being closed in the sending position and open in the receiving position.

WILHELM RUNGE. 

